1. Field of the Invention
The present invention relates to a cooling process for liquids, and specifically, a cooling process for liquids utilizing a coolant liquid that is chilled during off-peak electrical demand periods.
2. Description of the Related Art
Cow's milk as it comes from the cow has a temperature of over 90 degrees Fahrenheit. At this temperature, bacteria multiply with great rapidity. Thus, milking operations in most states are controlled by strict regulations, requiring for example, that bulk milk shall be cooled to 38-40 degrees Fahrenheit within two hours of milking. Consequently, in order to comply with state requirements pertaining to the cooling of milk, the majority of dairy farms operate costly refrigeration equipment on a 24-hour basis.
In order to avoid inefficient consumption of energy while cooling milk or other liquids, it would be advantageous for cooling processes to employ the use of thermal storage, whereby heat is extracted from a thermal reservoir during one time period and, during a different time period, the reservoir is used to extract heat from a different environment. In this manner, electricity usage is shifted from a peak demand period to an off-peak period. This shift assists commercial power generation companies to handle peak electricity usage, especially in major metropolitan areas where the peak power demand on the power generation of a utility on a very hot day can put a severe strain on the power generation system. Furthermore, shifting electricity usage to off-peak periods such as nighttime hours, allows significant cost savings to the consumer, as less expensive electricity is generally available at night and lower ambient temperatures allow for more efficient heat rejection.
Pre-cooling the liquid prior to directing it into the storage tank is another method by which energy can be conserved. Pre-cooling liquids minimizes the rise in temperature associated with mixing high temperature liquid with already cooled liquid that is in the storage tanks. As such, instead of placing a liquid directly into a storage tank, it is more energy efficient to pre-cool the liquid to a temperature approaching that of the storage temperature before directing it into the storage tank in order to refrigerate what may be a large quantity of liquid over a smaller and lower temperature range, rather than cooling the same quantity of liquid directly in the storage tank over a large temperature range.
Related art cooling processes have failed to achieve a simplified cooling process which fully realizes the potential for increased energy efficiency by neglecting to incorporate use of thermal storage, a pre-cooling step, or an effective combination of both processes.
U.S. Pat. No. 2,024,639, issued Dec. 17, 1935 to O. Greene, discloses cooling raw milk in a process wherein the raw milk is cooled by passing it as a thin film over the walls of a storage tank encircled by a refrigerant-filled jacket. As the storage tank for the milk also serves as the cooling unit, this cooling process relies heavily on constant refrigeration and is subject to the drawbacks mentioned above associated with cooling systems which lack a separate pre-cooling phase before the milk is directed into the storage tank.
U.S. Pat. No. 2,495,625, issued Jan. 24, 1950 to W. Bodinus, discloses a cooling process for wort involving a plurality of steps, including using water for cooling wort in the pre-cooling and intermediate stages and then for condensing refrigerant used in a third cooling stage. This process, while incorporating a pre-cooling phase, remains significantly dependent on a continuously operated refrigeration machine.
International Patent No. WO 98/15787, published Apr. 16, 1998, discloses a cooling system particularly, but not exclusively, for milk, which is transferred from a milking station to a vat along a first flow path and then exits the vat along a second flow path in which the milk is cooled before reentering the same vat. In this process, pre-cooling of milk is not employed and constant operation of a refrigeration unit is required.
U.S. Pat. No. 4,130,996, issued Dec. 26, 1978 to G. M. Sult, describes a bulk-milk cooling reservoir with an evaporation unit inside the reservoir and a condenser for recycling water to the evaporation unit. U.S. Patent No. 4, 351,271, issued Sep. 28, 1982 to Mueller et al., discloses a refrigerated receiver for an automatic milking system having an improved plate type heat exchanger inside the receiver for pre-cooling the milk. U.K. Patent No. 2,046,073, published Nov. 12, 1980, teaches a milk pasteurization apparatus and method, including heating and cooling the milk.
In addition to cooling milk and other liquids, an off-peak cooling system can be used in cooling any fluid. Air conditioning systems often use heat exchangers to transfer heat from the ambient air in a building to some other moving fluid, whether air, water or refrigerant. Before entering the heat exchanger, this moving refrigerant fluid must be cooler then the ambient building air in order for heat to transfer from the ambient air to the refrigerant. This heat transfer then raises the temperature of the refrigerant after is passes through the heat exchanger. When using a closed loop system, where the refrigerant liquid is recycled through the heat exchanger repeatedly, the refrigerant must be re-cooled in each cycle before entering the heat exchanger.
The re-cooling of the refrigerant requires a great deal of energy consumption. Air conditioning systems are generally run during the hottest hours of the day, which coincides with the peak energy demand hours of most electrical power plants.
Again, this peak energy use has two typical consequences. First, power companies often charge more for energy used during peak hours, raising the cost of air-conditioning buildings during these hours. Second, heavy air conditioning use over a highly populated area during peak hours can require more energy than some power plants are able to provide, creating a brown-out and shutting down the electrical supply for all users whose electricity is supplied by the overworked power plant.
A need exists for an air conditioning system that allows for the cooling of the recycled refrigerant to occur only during off-peak electrical demand hours. None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a chilled water storage tank system for an air conditioning process solving the aforementioned problems is desired.